Chapter 23 – Sections 1, 2, and 3

Weathering Processes

The change in the physical form or chemical composition of rock materials exposed at the earth’s surface is called weathering.

Weathering Process

There are two types of weathering:

Mechanical weathering, physical breakdown of rock

Chemical weathering, change in the chemical composition of rock

Weathering Process

Common agents in mechanical weathering are:

Ice Running water Gravity Wind Plants Animals

Ice Wedging

Ice wedging is a common form of weathering in northern climates.

Water seeps into cracks and as the water freezes it expands.

This splits the rock.

Plants and Animals

Organic activity is also a common cause of weathering.

Plant roots break through rock as they grow.

Ground burrowing animals expose new rock surfaces to weathering as they dig.

Running Water

Abrasion is the process of weathering by which friction scrapes rock away.

Niagara falls recedes 3ft per year.

Wind High winds pick up sediments and

displace them throughout large areas.

These sediments come in contact with other structures and start breaking them down.

Gravity

Surface creep is the slow movement of soil and rock debris by gravity

Fresh Water

Chapter 23.1

Groundwater

Most of Earth’s liquid fresh water is in the form of groundwater.

Other sources of fresh water are lakes, streams, glaciers, and water vapor (clouds) in the atmosphere.

The Water Cycle

The Water Cycle

The water cycle is made up of several processes, including evaporation, transpiration, condensation, precipitation.

The energy of sunlight and the force of gravity power the water cycle

Evaporation

Solar energy causes water on Earth’s surface evaporate

Liquid Gas Where does most water evaporate

from?

Transpiration

Some water vapor enters the atmosphere when it is released from the leaves and trees and other plants in a process called transpiration.

Condensation

Warm air rises, then it expands and cools Cool air holds less WV than warm air so

condensation occurs Water vapor forms droplets on small

particles in the air At low temps, ice crystals forms These droplets and ice crystals form

CLOUDS Gas Water Vapor

Precipitation

Gas Liquid Water droplets and/or ice crystals in

clouds get to heavy and fall back to Earth.

What force causes the precipitation to fall back to Earth?

Quick facts on The Water Cycle 90% of ocean water that gets 90% of ocean water that gets

evaporated into the atmosphere evaporated into the atmosphere falls back into the oceans as falls back into the oceans as precipitation.precipitation.

The other 10% falls and becomes The other 10% falls and becomes frozen in glaciers or falls on frozen in glaciers or falls on landmasses and becomes landmasses and becomes surface water again or ground surface water again or ground waterwater.

Fresh Water

A small portion of Earth’s fresh water is located in the atmosphere, streams, and lakes.

The majority is located in groundwater and glaciers

Water in the Atmosphere

How does water enter the Atmosphere?

What happens to water after a few hours or a few days of being in the atmosphere?

Water in Streams and Rivers When precipitation hits land it either

enters as groundwater or becomes runoff.

What is runoff?

Runoff and some ground water make their way to streams and rivers.

Streams and Rivers cont’

Rivers and large streams have many smaller streams called tributaries that flow into it. Tributaries collect runoff and

groundwater and transport it to River Systems

Water in Ponds and Lakes

What is the difference between a pond and a lake??

Contribute less than .7% to the amount of water in the world.

Water beneath the surface Ground water contributes to

approximately 25% of all freshwater found in the world

The Saturated Zone

A region underground where the pore spaces and cracks are completely filled with water.

The top of the saturated zone is called the water table

Example on page 707 in book

Saturated Zone cont’

As water flows through the saturated zone it passes through soil and rocks.

What is a rock said to be if water can easily pass through it?

Glaciers and Ice Bergs

Glaciers form in areas where more snow falls than melts each year. As snow builds up it compacts layers below, changing it into ice.

Icebergs are large pieces of ice that break off when a glacier reaches the ocean.

Class work/Homework

Read chapter 23.1 and answer questions 1-7 of the section assessment.

Chapter 23.3

How Water Shapes the Land

Pg 713-717

Gravity

Gravity is the main component of erosion.

In reference to water (streams/rivers), how does gravity help deposit sediment in different locations throughout a given area?

Deposition: the process in which sediments is laid down in new locations.

Deposition

The process in which sediment is laid down in new locations.

Running Water Erodes the Land Saltation: the process of particles bouncing along a

stream bottom Large- stay close to river bed Medium- drift and bounce Fine- float and drift A stream’s ability to erode depends mainly on its

_______________________.

Features Formed by Water Erosion Water erosion forms:

V-Shape Valleys Waterfalls Meanders Oxbow Lakes

V-Shaped Valleys

As a stream erodes the rock of its streambed, it causes the valley’s sides to become steeper.

Mass Movement down stream causes the sharply angles sides to form.

Flood Plains

The flat area along a stream that is entirely covered only during flood times.

Flood Plains cont’

Meanders: cause sediments to build up along a river where water moves more slowly. Over time, this process

forms loop-like bends in the river.

Oxbow Lake: sediments build up along channel , cutting the old meander off from the rest of the river

Groundwater Erosion The process of chemical

weathering causes much groundwater erosion, including the formation of caves and sinkholes.

If the water drips from the caverns ceiling, an icicle-like formation called a stalactite grows.

If the water drips down to the floor, a pillar of minerals called a stalagmite forms